1. Field of the Invention
This invention relates generally to electrically operated devices and more particularly to an improved solenoid device which may assume the form of a solenoid actuator or solenoid valve.
2. Prior Art
Simply stated, a solenoid device comprises an electrical coil which, when energized, produces an electromagnetic field that is utilized to perform some function. In the case of a solenoid actuator, the electromagnetic field is utilized to move a magnetic armature. A solenoid valve is essentially a solenoid actuator for controlling fluid flow.
U.S. Pat. No. 4,603,832 discloses a solenoid valve. The solenoid valve illustrated and described in the patent is a pilot valve for actuating a primary pilot controlled valve. This primary valve has a valve diaphragm which is movable into and from contact with a valve seat to control fluid flow through a flow passage in the primary valve. One side of the diaphragm is exposed to the fluid pressure in the valve passage. The other side of the diaphragm is exposed to the fluid pressure in a pilot chamber which is in constant communication with the primary valve passage upstream of the diaphragm valve seat. The chamber communicates with the primary valve flow passage downstream of the valve seat through the solenoid pilot valve. Closure of the solenoid pilot valve equalizes the fluid pressures across the valve diaphragm and creates an unbalanced fluid pressure force across the diaphragm which closes the diaphragm to block flow through the primary valve. Opening of the solenoid pilot valve bleeds fluid from the pilot chamber to reduce the pressure in this chamber and effect opening of valve diaphragm by the inlet fluid pressure.
The solenoid valve described in the above patent has one deficiency which is encountered if the solenoid coil fails, as can happen, and must be replaced. This deficiency resides in the fact that the valve comprises an assembly of relatively costly parts in addition to the solenoid coil, including a magnetic yoke for the coil and an inner armature assembly, which are permanently joined to one another. As a consequence, replacement of a failed solenoid coil requires replacement of the entire, relatively costly solenoid valve assembly.
This deficiency of the patented valve is alleviated to some extent in another known solenoid valve. In this latter known valve, the solenoid coil is removable from the inner armature assembly so that the armature assembly need not be replaced with the coil. However, the replaceable part of the solenoid valve includes, in addition to the coil, a magnetic yoke for the coil and a separately formed outer can or housing which includes an internally threaded female mounting coupling for the valve and is filled with an epoxy encapsulating both the coil and yoke. Accordingly, the replaceable part of this known valve includes the solenoid coil, the can and its female coupling, and the magnetic yoke, and is thus relatively costly.
Another deficiency of at least many existing solenoid devices of the character described resides in the fact that they are difficult to mount in the way which is the most desirable or convenient for a particular application. For example, it is often desirable or neccessary to mount a solenoid valve on a wall with the solenoid located at one side of the wall and the solenoid leads extending to the opposite side of the wall. With conventional solenoid valves this presents not only the problem of attaching the solenoid to the wall but also the additional problem of providing a hole in wall through which the solenoid leads may pass to the opposite side of the wall. These problems are compounded if the wall forms a barrier between a hostile environment, against which the solenoid coil and armature are sealed, but not the solenoid leads, and a non-hostile environment. Many of the existing solenoid valves and other solenoid devices are not well adapted for or are totally incapable of use in these situations.
Accordingly, there is a need for an improved solenoid valve which if free of the above and other deficiencies of the existing solenoid valves. As will become evident from the ensuing description, this same need exists with respect to other types of solenoid devices, such as solenoid actuators, which are subject to at least some of the same deficiencies.